Hot-melt adhesive composition containing glycerol ester of fumaric-modified rosin

ABSTRACT

Hot-melt adhesive composition consisting essentially of a substantially linear polyamide resin, having an average molecular weight between 3,000 and 10,000 and a Ball and Ring softening point between 45* and 190* C, and between 5 and 30 parts by weight of glycerol ester of fumaric-modified rosin for each 100 parts by weight of the linear polyamide resin; with a preferred composition containing between 10 and 20 phr of the glycerol ester of fumaric-modified rosin and up to 10 phr of a petroleumderived wax selected from the group of paraffin and microcrystalline waxes.

nite States aten [191 1 it? et all. [45] Jan, 22, 1974!. t

[54] HOT-MELT ADHESIVE COMPOSITION 3,253,059 5/1966 Vollrner....'260/897 CONTAINING GLYCEROL ESTER OF OTHER PUBLICATIONS FUMARIC-MODIFIEDROSIN The United States of America as represented by the Secretary ofAgriculture, Washington, DC.

Filed: Feb. 27, 1970 Appl. No.: 15,233

Assignee:

US. Cl. 260/24, 260/28 Int. Cl C08c 9/18, C08d 3/40 Field of Search260127, 28.5 A, 24

References Cited UNITED STATES PATENTS 4/1968 House 260/27 l-labrook etal. Industrial and Engineering Chemistry I958, pp. 321 and 322.

Primary Examiner-Donald E. Czaja Assistant Examiner-William E. Parker 57] ABSTRACT Hot-melt adhesive composition consisting essentially of asubstantially linear polyamide resin, having an average molecular weightbetween 3,000 and 10,000 and a Ball and Ring softening point between 45and 190 C, and between 5 and 30 parts by weight of glycerol ester offumaric-modified rosin for each 100 parts by weight of the linearpolyamide resin; with a preferred composition containing between 10 and20 phr of the glycerol ester of fumaric-modified rosin and up to 10 phrof a petroleum-derived wax selected from the group of paraffin andmicrocrystalline waxes.

6 Claims, N0 Drawings HOT-MELT ADHESIVE COMPOSITION CONTAINING GLYCEROLESTER OF FUMARIC-MODIFIED ROSIN A non-exclusive, irrevocable,royalty-free license in the invention herein described, throughout theworld for all purposes of the United States Government, with the powerto grant sublicenses for such purposes, is hereby granted to theGovernment of the United States of America.

This invention relates to hot-melt polyamide-resin adhesive compositionswhich are applied hot to various substrates and which upon cooling forma bond adhering the substrates together. More particularly, theinvention concerns a hot-melt adhesive composition consistingessentially of a polyamide resin and between and 30 parts by weight ofglycerol ester of fumaricmodified rosin for each 100 parts by weight ofthe polyamide resin.

Hot-melt adhesives are bonding materials known to be applied hot andupon cooling to the solid state to form a bond between substrates.Application of heat to a hot-melt adhesive brings it to a liquid state,and after removal of the heat it sets by merely cooling. Where thecooling is rapid, nearly instantaneous bonding is possible. The hot-meltadhesive system frequently offers increased production speeds and lowercosts than other adhesive systems. In general, useful hot-melt adhesivecompositions are essentially thermoplastic, allsolid material with nosolvent being used therewith. 1n the past, a large number of natural andsynthetic waxes and resins have served as principal constituents invarious useful hot-melt adhesive compositions. The natural waxes andresins typically have low strength and melt easily to low viscosityfluids. Generally in hot-melt adhesive these natural materials areblended with various proportions of higher strength and high molecularweight synthetic resins, such as polyamides, polyvinyl acetate,ethylene-vinyl acetate, or the like. In such compositions the syntheticresin acts as a film former imparting the principal adhesion strengthand the natural resin serves to lower the adhesives cost and is usefulalso therein to improve certain desirable properties of the hot-meltadhesive system. Many adhesives also contain minor amounts of otherconstituents for improving film formation, imparting tack, flexibility,gloss, and the like. Desirable properties in a hot-melt adhesive are itsadhesion strength to various substrates, heat stability at itsapplication temperature for a prolonged period, i.e., useful pot life,ability to adequately wet the substrates to which it is applied,flexibility in its solid state, block resistance, and the likeproperties. Although various useful hot-melt adhesive compositions areknown, there has continued to be a need for other and additionalhot-melt adhesive compositions offering lower cost formulations andequivalent and/or improved properties and containing materials hithertonot known to be useful in such compositions. It is to fulfilling thoseneeds that the present invention is directed.

The hot-melt adhesive composition of the invention is based on asynthetic polyamide resin in which resin functions as the principalfilm-former and tackifying constituent and the glycerol esters offumaric-modified rosin which glycerol esters function to impartadditional tack, flexibility, lower viscosity, and lower cost to thecomposition. The inventions hot-melt adhesive composition, in relativeproportions by weight for each parts of the polyamide resin, consistsessentially of the linear polyamide resin or resin mixtures and between5 and 30 parts of the glycerol esters of fumaricmodified rosin. Apreferred embodiment of the composition also contains up to 10 parts byweight, based on each 100 parts by weight of polyamide resin, of apctroleum-derived wax, i.e., paraffin or microcrystalline wax, to lowerviscosity, impart improved smear and blocking resistance, and the like.It may also contain minor amounts of various ancillary constituentsknown to the art as useful, in conventional hot-melt polyamide-resinadhesive compositions.

The polyamide resins used in the composition are thermoplastic reactionproducts of dibasic acids with diamines and are well known in thehot-melt adhesive art. The particular dibasic acids used for preparationof these polyamide resins are polymerized fatty acids or dimer acids,made by polymerizing unsaturated fatty acids. These dimer acids consistessentially of a mixture of about 36 carbon atom dibasic acids, andusually also contain several isomeric dimers together with a smallamount of trimer and higher polymers. When these dibasic acids arecondensed with diamines, usually ethylene diamine or anotherlow-molecular weight aliphatic or aromatic diamine, there are providedpolyamide resins ofa generally linear nature and a relatively neutralcharacter. Here, a relatively neutral character means there are veryfewremaining unreacted amino and carboxyl groups and, in the polyamideresin molecules, the quantities of each of the reactant moieties areapproximately equaLln general, these useful polyamides are relativelyhigh-molecular-weight (av. -3,000 to 10,000) thermoplastic resinsproviding an exceptional combination of properties including outstandingadhesion to a variety of substrates, high levels of tensile strengthwith good elongation, high bond strength, flexibility and toughness, lowwater absorption, and retention of physical properties on aging. Presentcommercially available polyamide resins for hot-melt adhesiveformulations, and those polyamide resins also useful in the composition,have B&R softening points between about 40 and 190 C. Althoughfrequently only one polyamide resin is employed as the principalconstituent of the hot-melt adhesive composition, if desired a blend ofseveral of the polyamide resins may be employed.

1n the preferred adhesive composition of the invention there is includedup to about 10 parts by weight of a petroleum-derived paraffin ormicrocrystalline wax for each 100 parts by weight of the polyamide resinincluded in the composition. Crystalline or paraffin wax is derived fromdewaxing of distillate lubricating frac tions and microcrystalline waxfrom dewaxing the residual lubricating fractions of the crude petroleum.The paraffin waxes generally have a melting point in the range of F,while the microcrystalline waxes have a melting point in the range of150 vF. The paraffin waxes consist essentially of straightchainhydrocarbons of about 26-30 carbons per molecule. The microcrystallinewaxes consist essentially of branched-chain hydrocarbons of about 41-50carbons per molecule. In the adhesive composition of the invention, theutilization therein of a petroleum-derived paraffin or microcrystallinewax serves to lower viscosity at hot-melt application temperatures,provides smear and blocking resistance, and advantageously improveswetting of polyester substrates, such as polyethylene terephthalatefilms. In the composition of the invention the petroleum-derived waxemployed therein has a melting point no higher than the 884R softeningpoint of the polyamide resin included therein.

Essential to the hot-melt adhesive composition of the invention isinclusion therein of between 5 and 30 parts by weight, preferablybetween about l0 and 20 parts by weight, of the glycerol esters offumaric-modified rosin for each l00 parts by weight of the polyamideresin included in the adhesive composition. Incorporation of theglycerol esters of fumaric-modified rosin in the adhesive compositionserves to lower the cost thereof and improves a number of thecompositions properties desirable for hot-melt adhesive applicationpurposes. The employed glycerol esters of fumaric-modified rosin ingeneral are the esterification product of fumaricmodified rosin andglycerol to provide substantially complete esterification of allcarboxyl groups of the fumaric-modifled rosin. The esterification is byconventional techniques and processes, and utilizes glycerol in from astoichiometric amount up to about 25 percent excess glycerol to reactwith all carboxyl groups of the fumaric-modified rosin. As used herein,the term rosin includes gum, wood, and tall-oil rosins. Afumaricmodified rosin in general is the Diels-Alder condensation productof rosin with fumaric acid in an amount between 4 and parts by weight,preferably 8 and 12 parts by weight for each 100 parts by weight of therosin. The major product of the Diels-Alder type condensation of fumaricacid with rosin is the tricarboxylic acid, trans-6,l4-dihydrolevopimaric-acid-endo-a,B- succinic acid. The preparation offumaric-modified rosin is taught in Industrial and EngineeringChemistry, Vol.50, No.3, pg. 322-2, March 1958, by Noah J. Halbrook, eta]. and also in J. Am. Chem. Soc. 80, 368-70 1958) by Noah J. Halbrooket al. Desirably the preparation of the fumaric-modified rosin, which issubsequently esterified with glycerol is carried out at the reactionconditions which provide for substantially complete reaction of all ofthe fumaric acid reactant.

Although not essential thereto, the hot-melt adhesive composition of theinvention also may contain minor amounts of various other and ancillaryconstituents as are known to the art in conventional amounts and forpurposes well known in hot-melt adhesive compositions containingpolyamide resins. These useful ancillary constituents include fillers,pigments, dyes, stabilizers, antioxidants, and the like. Pigments, dyes,fillers, and the like may be used to obtain colored or opaque adhesivesand to reduce cost or to impart firmness. lllustrative of fillers aretitanium dioxide, clay, diatomaceous earth, and the like. To avoiddiscoloration, gelation, or physical separation of the compositionsconstituents during excessive or prolonged heating of its melt state,stabilizers may be included. Illustrative of these stabilizers aresodium benzoate, calcium stearate, sodium sebacate, and the like. Whenused in the hotmelt composition, the sum total of all the variousincluded ancillary constituents generally will not exceed about 25percent by weight of the composition, and of course the amount of eachincluded should not appreciably detrimentally effect the adhesiveproperties of the composition to such an extent as to render thecomposition not useful for the particular hot-melt application beingcontemplated.

In general, the hot-melt composition of the invention is prepared simplyby melting and mixing together its lower me l ting constituents, andthen adding and mixing therein the high-melting constituents, at atemperature above its nielting' point. its pEp ara'tiQ n 'aSPec tSclosely approximate those conventional in preparation of the prior arthot-melt adhesive compositions. Thus one may employ extruders,kneading-type mixers, varnish kettles, or other like equipment suitablyprovided with heating means, e.g., oil or steam jackets, electric coilheaters, etc.

The glycerol esters of fumaric-modified rosin, which are included in thecomposition of the invention, will be more fully understood from theseveral illustrative preparations thereof which follow.

EXAMPLE A In this sample a commercial grade, WW gum rosin of acid number165, color grade WW, and having a content of 60 percent by weightabietic acids is used and condensed with 10 parts of fumaric acid perparts of the rosin to provide the fumaric-modified rosin whichsubsequently is esterified with glycerol in accordance with thefollowing procedure:

A 5-liter, 3-necked flask is charged with 2,000 grams of the rosin. Theflask is equipped with a stirrer, dropping funnel, inert gas inlet,thermometer, short aircooled condenser and water trap, topped with awatercooled condenser. The rosin is heated to 200 C with slow stirringunder a nitrogen-gas sweep of 5 to 10 ml per minute. After the waterforming on heat-up is removed, 200 grams of fumaric acid is addedslowly, to prevent frothing. The condensation is slightly exothermic.Heating at 200 C with stirring under a blanket of nitrogen gas iscontinued for 1 hour. The resulting fumaric-modified rosin, yield 2,184grams, has an acid number of 233, USDA color grade WG. The trap containsabout I 1 ml. of water and 6 ml of oil.

A 10 percent excess of glycerol over the stoichiometric amount to reactwith all of the carboxyl groups present in the fumaric-modified rosin isemployed for esterification. This is calculated as follows:

. 2. E L iEQH Pete s"? Qt itt. 2 3 32.3l56l=l33.5 mg. glycerol per gramof rosin 133i'5' 218 i 293.0g (10 percent of 293 322 g. of glycerolThus, 322 grams of glycerol is added to the flask and the nitrogen flowadjusted to about 30 ml per minute. Over a four-hour heating period thetemperature is gradually increased from 200 to 275 C. During this timethe acid number drops to 37. The temperature of 275 C is held for anadditional 1 .5 hours. The resulting glycerol esters of fumaric-modifiedrosin have an acid No. 12.5, Ball and Ring softening point 127 C, USDAcolor grade WG.

During the entire preparation there is collected in the trap about 200grams of which ml are water and 35 m] are oils. The materials balance onthe basis of em- :ploying 2,000 grams of rosin, 200 grams of fumaric"acid, and 322 grams of glycerol for a total of 2,522 grams of reactantsless the 200 grams water and oils collected in the trap calculates for aproduct weight of 2,322 grams. Actual yield of glycerol esters offumaricmodified rosin is found to be 2,313 grams with an unaccountedloss of 9 grams.

EXAMPLE B The preparation described in Example A is followed exac tlyexcept that in preparing the fumaric-modified corresponing decrease iscalculated in the amount of glycerol used. The resulting glycerol esterof fumaricmodified rosin has a Ball and Ring softening point of 99 C.

EXAMPLE FORMULATION 1, 2, AND 3 There are prepared the following basicformulations, containing a polyamide resin and the glycerol esters offumaric-modified rosin, to illustrate embodiments of the hot-meltadhesive composition of the invention.

Formulation i 2 3 Parts by weight of the glycerol l0 I5 20 ester offumaric-modit'icd rosin for each 100 parts by weight of the polyamideresin Ingredients Polyamide Resin. soft.pt-l05C 50 50 Glycerol Esters ofFumaricmodified Rosin 5 7.5 10 Paraffin Wax, m.p.-I34F 2.5 2.5 2.5

kettle. The kettles contents are heated to about 275 35 to 285 C withstirring and held at that temperature until the charge is molten andappears to be a uniform composition; generally this requires betweenone-half to 1 hour. The polyamide resin then is added and mixed thereinuntil the composition again appears to be a molten mass free of lumpsand the like. If desired, the composition may be permitted to cool andto solidify and then at a later time reheated to a molten state forapplication as a hot-melt adhesive. Otherwise the composition ismaintained and/or brought to a suitable temperature, generally about 140F, for hot-melt application and utilized.

To illustrate utility and advantageous properties exhibited by theforegoing illustrative basic formulations as embodiments of hot-meltadhesive compositions of the invention, a number of physical propertiesare determined for compositions of these formulations and for thecompositions utilized to bond various adherends by hot-melt techniques.For comparison therewith there also are prepared in a like manner thesame formulations, except that no glycerol esters of fuma'ricmodifiedrosin are included therein and except that the 6 re'ara'zaaaaasegaakvagarsas iaa"many stabilized ester of a completely hydrogenatedrosin such as Fora] I and by the pentaerythritol ester of partiallyhydrogenated rosin, and then in a like manner various physicalproperties determined for these comparison formulations and theirbonding of adherends.

The following tables I through lV present illustrative physicalproperties determined for a number of composition embodiments of theinvention along with corresponding data determined on the just-mentionedcomparison formulations. Details on preparation of samples fordetermination of the reported property data along with description ofthe tests conducted also are presented. Peel strength illustrates thecomparative peel or 5 stripping of the adhesive bond. The peel strengthis the average load per unit width of bond line required to separateprogressively one member from the other over the adhered surface at aseparation angle of approximately 180 and at a separation rate of 12inches per minute jaw speed. Samples prepared for the peel strength testare laminated in a press at 300 F, psi, for 5 to 10 seconds. The samplesare placed between two stainless steel plates of one-eighth inchthickness. Twp sheets of l 0 mil tetrafluoroethylene polymer are usedbetween thes tainless steel plates and the samples.

This was done to aid in removal of samples should hot melt adhesive geton the plates during lamination. The peel strength of the adhesive bondis evaluated using ASTM Method D903-49 except that the number of testspecimens is reduced to two.

The wettability of the adhesive on the substrate is determined by avisual check, rating the specimens excellent, good, fair, or poor.

A modification of TAPPl Method T454ts-66 is used to determine theflexibility of the film of hot-melt adhesive. Films of adhesive aredrawn down on 60-pound all-purpose litho paper. A modification of TAPPlMethod T465sm-52 is used for creasing the paper with an approximate2-mil thick hot-melt adhesive film. The weight used to crease thespecimens is 1 kg per 5 linear centimeters. With the hot-melt side up ona table a 3- inch diameter, clear plastic tube, approximately 3 incheshigh, is placed on each specimen. Sand is placed in the cylinder to adepth of one inch. The same is saturated with corn oil which has beendyed blue with oil blue NE. The dyed oil penetrates the specimenwherever there is a break in the hot-melt film. After 16 hours at roomtemperature, the samples are evaluated on a rating scale of excellent,very good, good, fair, or poor. An excellent rating indicates nopenetration of dyed oil, and a poor rating indicates that the undersideof the 4-inch square had more than 50 percent of its area colored withthe dyed oil.

The block resistance of the hot-melt systems is determined by TAPPlMethod T477m-47. The tests are run at F in an uncontrolled humidityovenat 0.5 psi.

The viscosity of the hot-melt adhesives is determined glycerol esters offumaric-modifiecl rosin constituent is 1 3 5 C I p g m TABLE I PeelStrength AdhesionJLl Polyethylene Laminate: After Heat- Terephthalate40-Lb Kraft Stability Hot-Melt Adhesive Concentration. Film 40-Lb KraftLiner Board] Test' on Composition Containing: phr' Liner Board AluminumFoil Polyester Film No Rosin or rosin de i at ve a-.. 0

Peel Strength Hot-Melt Adhestve Concentration, ilm 40-Lb KraftComposttton Contatntng: phr Liner Board Aluminum Foil Polyester m V bFilm jighly stabiliaedester V MW of completely hydrogenated rosin" 104.7 2.4 7.5 6.4 Pentaerythritol ester of partially hydrogenated rosin"10 3.4 1.4 3.0 2.6 Glycerol esters of fumaricmodified gum rosin of Ex. Ain Form. 1 l0 5.6 2.5 4.8 5.5

"' pli pounds per linear inch. average of at least 2 specimens.

controls [8 hours at 350F. using agitation pli pounds per linear inch.average of at least 2 specimens phr parts by weight of rosin derivativeper hundred parts by weight of I pairts welght ofa pO-lyamlde resln of agen- Pfllyumids with erally linear nature, a relattvely neutralcharacter, Adhesive composition is coated on a polyethyleneterephlhalate film with a brass. drawn-down bar on a stainless-steeL 280F. hot-plate to a coating thickness of havlng an average molecularweight wlthln the 1 mils. Specimens then are laminated in a Preco pressat 300 F. lUU psi, for ll] range f 3 d a d softerb see S ecimens areplaced in a constanbtemperature room (73 F. 50 percent o I relatttehumidity] for 7 days before lng [301m betwfien and C., and being g fgfiffi ifs thermoplastic reaction product of a mixture of 7 ill il SpLLtiQiilz in./min y w 7 dimer acids consisting essentially of a mixture ofTABLE Ill I In addition to the preceding illustrative embodiments of thecomposition of the invention, one similarly can employ each of theglycerol esters of fumaric-modified rosin of Example B and C in each ofthe basic formulations 1 through 3 and obtain other illustrativeexamples of the composition of the invention. While the properties ofsuch prepared additional compositions will not necessarily be identicalto the property data determined and reported in the foregoing tables, itwill be found that on the whole each of these prepared hotmelt adhesivecompositions exhibit adequate properties to enable the composition to beuseful in hot-melt adhesive bonding application.

We claim: 1. A hot-melt adhesive composition comprising:

Viscosity Values for the Polyamide System Viscosity at l35C Hot AdhesiveConcentration, Before Heat- After Heat- Composition Containing phr"Stability Test Stability Test No rosin or rosin derivative 0 52.35 77.33

Highly stabilized ester of completely hydrogenated rosin'" l0 44.02|()4.7()

Pentaerythritol ester of partially hydrogenated ros in' 10 50.56 58.89

Glycerol esters of fumaricmodified gum rosin of Ex. A.

in Form. 1 10 65.91 I 74.36 mm M phr parts by weight of rosin derivativeto a hundred parts by weight polyamide resin.

' controls 1 i i 7 k g TABLE.

7 Hot-Melt Adhesives Data Concen- B e fore Ai'ter Wettahility Test"Hot-Melt Adhesive ti-ation S ability Stability" Sample Sample BlockingMy- 40 60 Al Containing phr Test Test l 2 Test" lar RLB APL Foil Norosin or rosin Straw Light ,7 derivative 0 yellow lgroyv n D 3 4 4 3 3aste t ni cc ,4 um Flexibilit of Co lor g f ljgt-Me t" mgh'F fi-Wettability Test Concen Before lite r M Hot-Mellg hesi e tration S bilitStabfiity Sample Sample Blocking My- 40 60 Al gontaining V v phr TestTest 1 2 Test" lar RLB APL Foil Highly stabilized ester of completelyhydro- Straw Dark red generated rosin" l yellow brown E E 4 4 4 3 3Pentaerythritol ester of partially hydro- Straw Dark red genated rosin"l0 yellow brown E E 4 3 4 3 3 Glycerol esters of fumaricmodified rosinof Ex. A Brownish Dark red in Form 1 yellow brown E E 4 4 4 4 3Stability test was run at 280 F for IE hours using agitation,Flexibility ratings E=exccllcnt. VG=very good Blocking test was run atlF for 24 hours at 05 psi. Blocking ratings: 4=complctc, 3=considcruhle,2=slight, l=no Substrate abbreviations: Mylar=Mylar film (l' /a mil), 40KLB=40-lh. Kraft liner board, 60 APL=60 lh all purpose litho paper, AIFoil l mil pure aluminum foil.

Wettability ratings: 4 excellent. 3 good, 2 fair I poor Applied coatingweights in lbs/I00 ft"; on Mylar-8 6 on 40 KLB 24.l. on 60 APL 212, andon Al Foil ll,l.

" controls.

about 36-carbon atom dibasic acids with a lowweight aliphatic oraromatic diamine; molecular weight aliphatic or aromatic diamine; 25 b.10 to 20 parts by weight of glycerol esters of fuand maric-modifiedrosin, which glycerol esters are b. between 5 and parts by weight ofglycerol esters prepared by reacting a fumaric-modified rosin se- OffumiHiC-mOdifi d rosinlected from the group consisting of fumaric- 2.The composition of claim 1 which also includes up difi d gum rosin, f idifi d Wood rosin, to 10 Parts by Weight of a Petroleum-derived Waxha\/- 30 and fumaric-modified tall oil rosin with sufficient ing amelting PQ no higher than the Ball and Ring glycerol to esterify thecarboxylic acid groups pres- Softening Point of the Polyamide resin andSelected ent in the fumaric-modified rosin, thereby to profrom tha groupConsisting of Paraffih Wax and microduce an essentially completelyesterified fumaric- Crystalline modified rosin substantially devoid ofanhydride g- 3. A hot-melt adhesive composition comprising: 100 Parts yWeight of a Polyamide resin Ofa g 4. The Composition of claim 3 whereinthe fumaricerally linear nature, a relatively neutral character, difi drosin i gum rosin having an average molecular Weight within the 5. Thecomposition of claim 3 wherein the fumaricrange of 3,000 to 10,000, aBall and Ring softening difi d rosin is wood msin.

point between and and being the ther- 6. The composition of claim 3wherein the fumaricmoplastic reaction product of a mixture of dimer difid rosin i taii Oii rosin acids consisting essentially of a mixture ofabout 36-carbon atom dibasic acids with a low-molecular =l

2. The composition of claim 1 which also includes up to 10 parts byweight of a petroleum-derived wax having a melting point no higher thanthe Ball and Ring softening point of the polyamide resin and selectedfrom the group consisting of paraffin wax and microcrystalline wax.
 3. Ahot-melt adhesive composition comprising: a. 100 parts by weight of apolyamide resin of a generally linear nature, a relatively neutralcharacter, having an average molecular weight within the range of 3,000to 10,000, a Ball and Ring softening point between 45* and 190* C. andbeing the thermoplastic reaction product of a mixture of dimer acidsconsisting essentially of a mixture of about 36-carbon atom dibasicacids with a low-molecular weight aliphatic or aromatic diamine; b. 10to 20 parts by weight of glycerol esters of fumaric-modified rosin,which glycerol esters are prepared by reacting a fumaric-modified rosinselected from the group consisting of fumaric-modified gum rosin,fumaric-modified wood rosin, and fumaric-modified tall oil rosin withsufficient glycerol to esterify the carboxylic acid groups present inthe fumaric-modified rosin, thereby to produce an essentially completelyesterified fumaric-modified rosin substantially devoid of anhydridegroups.
 4. The composition of claim 3 wherein the fumaric-modified rosinis gum rosin.
 5. The composition of claim 3 wherein the fumaric-modifiedrosin is wood rosin.
 6. The composition of claim 3 wherein thefumaric-modified rosin is tall oil rosin.